210 Mr. J. Prideaux's Expei-iments on Vanadiate of Ammonia^ 



being occasionally made to vibrate, by striking on the edge 

 with a steel blade. The salts were, however, left on the glass 

 in two successive coatings; and a film, which had formed upon 

 the liquor, was studded beneath with brilliant globules, in 

 which no facets could be discovered by the microscope. 



4. Vanadiate of ammonia is much less soluble, falling like 

 cream of tartar; it crystallized freely, on cooling, in acute 

 rhombic blades, like spear-heads. 



5. Vanadiate of lime is still less soluble than the last, and 

 also crystallized in cooling. Crystalline form not unlike the 

 other, but thicker. The crystals were, however, so irregular 

 that but kw could be defined. 



6. Vanadiate of barytes. A solution of 1*482 grains of 

 vanadiate of ammonia, containing an atom of water, was mixed 

 with a solution of \"i\2 grain of chloride of barium; the whole 

 fluid became full of coagula, which settled, by boiling, into a 

 heavy white power. The residual liquor. was evaporated and 

 tested in the usual manner, and the decomposition was found 

 complete, so far as could be ascertained by this mode. 



This precipitate affords a convenient method of recovering 

 the vanadic acid used in experiments. Mixing together the 

 various soluble vanadiates, solution of muriate of barytes 

 may be added, in slight excess, keeping the liquor hot. The 

 vanadiate of barytes will quickly subside, and may be readily 

 washed. It is then (whilst quite recent) to be thrown into 

 40 or 50 parts of water, with a little excess of sulphuric acid; 

 when it will assume the deep orange colour of bi-chromate 

 of potash. It may digest for half an hour, with occasional 

 shaking ; when carbonate of ammonia is to be added, a small 

 lump at a time, letting it dissolve gradually, and mixing up 

 the liquor well before each addition, till the liquor is neutral, 

 avoiding much excess of the carbonate. The precipitate will 

 then be white or will become so by boiling in the liquid ; and 

 after washing to remove the adhering solution will not be 

 discoloured by fresh sulphuric acid. The liquor will contain 

 sulphate and vanadiate of ammonia, which are to be separated 

 by crystallization. 



In the following experiments, solution of vanadiate of am- 

 monia was dropped into excess of the metallic solutions ; the 

 persulphate of iron was prepared by heating protosulphate in 

 a test-tube with nitric acid, and contained that acid in excess; 

 — the others were all pure. 



Immediate Effect. \ After 12 Hours. 



"A pulverulent yellowish- 

 white precipitate; the 

 liquid orange yellow. 



Green 



„ , C No precipitate; the liquid assumed 



P £? ^ ^ a greenish-vellow hue, becoming 

 ( gradually yellower and turbid. 



